1. Field of the Invention
The present invention relates to a camera having an auto-focussing device.
2. Related Background Art
Conventionally, as a method of photographing in a state in which images of objects located at a plurality of different positions are focussed, an aperture is determined by setting the camera in the state of a stopped-down aperture and the respective objects are made to be located within the depth of field, while the photographer confirms the state of the objects.
Accordingly, photographing in the above-described situation is substantially affected by the experience and the like of the photographer and is therefore unsuitable to an amateur, and there has been a high probability of this resulting in a failure.
In addition, a camera is known in U.S. Pat. No. 4,219,261 in which respective in-focus positions are determined by manually operating the lens with respect to two different objects, an aperture value is determined from a difference between the in-focus positions, and an in-focus state is obtained for both objects, thereby determining the aperture.
However, the aperture value thus determined by the above-described method is effective for the focal length of the lens at that point of time, but, if a zooming state of the lens is altered after determination of the aperture value, the depth of field changes, so that it is impossible to obtain an in-focus state for both objects with that aperture value. In addition, in the aforementioned U.S. Patent, the lens is operated manually, and its operational efficiency has been poor.
To overcome this problem, the present applicant proposed a camera which is adapted to automatically determine an in-focus state for each object using an auto-focussing device so as to determine the aforementioned aperture.